Question

我正在尝试在Swift 2中创建一个运行并获取AppleScript脚本结果的程序。

这是我的代码：

import Foundation

func runAppleScript(script:String) -> String
{
    let errorInfo = AutoreleasingUnsafeMutablePointer<NSDictionary?>()
    let startAtLoginScript: NSAppleScript = NSAppleScript(source: script)!
    let theDiscriptor:NSAppleEventDescriptor = startAtLoginScript.executeAndReturnError(errorInfo)
    let theResult:String = theDiscriptor.stringValue! //This is whats causing the error

    return theResult
}

let scriptResult = runAppleScript("tell app \"Spotify\" to playpause")

NSLog("\(scriptResult)")

问题是程序崩溃和输出：

致命错误：在解包可选值时意外发现nil

在控制台中。我也尝试了if let else，但这也不起作用。我该如何解决这个问题？

使用swift语言使用OS X命令行模板对此进行了测试。

Answer 1

实际上错误可能来自NSAppleScript(source: script)!，因此正确的解决方案是返回一个可选字符串，而不是使用强制解包：

func runAppleScript(script:String) -> String? {
    let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
    let startAtLoginScript = NSAppleScript(source: script)
    let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo)
    return theDescriptor?.stringValue
}

if let scriptResult = runAppleScript("tell app \"Spotify\" to playpause") {
    NSLog("\(scriptResult)")
} else {
    print("the script execution failed")
}

如果您在失败时更喜欢默认值而不是nil，则无需返回Optional：

func runAppleScript(script:String) -> String {
    let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
    let startAtLoginScript = NSAppleScript(source: script)
    let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo)
    return theDescriptor?.stringValue ?? ""  // if nil, returns the default ""
}

let scriptResult = runAppleScript("tell app \"Spotify\" to playpause")
NSLog("\(scriptResult)")

至于使用新的 Swift 2 错误处理系统，您在runAppleScript内使用的所有方法都没有抛出错误，因此只有在使用了自定义错误类型并自己抛出错误。例如：

enum MyAppleScriptError: ErrorType {
    case ExecutingScriptFailed
    case GettingStringValueFailed
}

func runAppleScript(script:String) throws -> String {
    let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
    let startAtLoginScript = NSAppleScript(source: script)
    guard let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo) else {
        throw MyAppleScriptError.ExecutingScriptFailed
    }
    guard let value = theDescriptor.stringValue else {
        throw MyAppleScriptError.GettingStringValueFailed
    }
    return value
}

do {
    let scriptResult = try runAppleScript("tell app \"Spotify\" to playpause")
    NSLog("\(scriptResult)")
} catch {
    print(error)
}

Swift 3

同样的想法，但是一些实现细节是不同的。

func runAppleScript(_ script:String) -> String? {
    let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?>? = nil
    if let startAtLoginScript = NSAppleScript(source: script) {
        let theDescriptor = startAtLoginScript.executeAndReturnError(errorInfo)
        return theDescriptor.stringValue
    }
    return nil
}

if let scriptResult = runAppleScript("tell app \"Spotify\" to playpause") {
    NSLog("\(scriptResult)")
} else {
    print("no return value")
}

错误处理：

enum MyAppleScriptError: ErrorProtocol {
    case ExecutingScriptFailed
    case GettingStringValueFailed
}

func runAppleScript(_ script:String) throws -> String {
    let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?>? = nil
    let startAtLoginScript = NSAppleScript(source: script)
    guard let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo) else {
        throw MyAppleScriptError.ExecutingScriptFailed
    }
    guard let value = theDescriptor.stringValue else {
        throw MyAppleScriptError.GettingStringValueFailed
    }
    return value
}

do {
    let scriptResult = try runAppleScript("tell app \"Spotify\" to playpause")
    NSLog("\(scriptResult)")
} catch {
    print(error)
}

Answer 2

我修复了自己的代码。

import Foundation

func runAppleScript(script:String) -> String
{
    let theResult:String
    let errorInfo = AutoreleasingUnsafeMutablePointer<NSDictionary?>()
    let startAtLoginScript: NSAppleScript = NSAppleScript(source: script)!
    let theDiscriptor:NSAppleEventDescriptor = startAtLoginScript.executeAndReturnError(errorInfo)
    if let _ = theDiscriptor.stringValue
    {
        theResult = theDiscriptor.stringValue!
    } else {
        theResult = ""
    }

    return theResult
}



let scriptResult = runAppleScript("")

我要做的是在解开之前检查theDiscriptor.stringValue是否有值。我得到的错误是因为我在打开包装后试图检查该值。只需删除支票上的!即可修复我的问题。

修改

在Swift 3中尝试此操作时，代码let errorInfo = AutoreleasingUnsafeMutablePointer<NSDictionary?>()不再有效。为了解决这个问题，我更新了代码。

func runAppleScript(script:String) -> String?
{
    var theResult:String?
    let startAtLoginScript: NSAppleScript = NSAppleScript(source: script)!
    var errorInfo:NSDictionary? = nil
    let theDiscriptor:NSAppleEventDescriptor = startAtLoginScript.executeAndReturnError(&errorInfo)
    if let _ = theDiscriptor.stringValue {theResult = theDiscriptor.stringValue!}
    return theResult
}

奖金

通过返回一个可选字符串，它允许您检查代码是否返回了值。

示例：

旧方式

let output = runAppleScript("script")
if output != ""
{
    //Script returned date
} else {
    //Script did not return data
}

新方法

if let output = runAppleScript("script")
{
    //Script returned data
} else {
    //Script did not return data
}

打开可选值时意外发现nil（AppleScript结果）

2 个答案: